1. Field of the Invention
Embodiments of the invention relate generally to medical laser systems and, more particularly, to devices and methods for multiple beam laser treatment in which tissue sites are simultaneously exposed to different laser types and laser wavelengths for improved therapeutic effect.
2. Description of Art
Lasers find application in a variety of medical and dental treatment procedures, with some of the most common operations involving the cutting, ablation, disinfection or other treatment of tissue. Depending on the particular wavelength, output power, pulse width of the laser emission, and the absorptivity of the target tissue, varying biological materials from soft tissue such as muscles and skin, to hard tissue such as teeth and bones, can be cut and ablated. Laser systems with output power levels up to the tens of watts can be used for these applications, although lower powered laser systems with output power levels in the 10 milliwatt range can be used in microbicidal applications, tissue biostimulation applications, low-level light therapy, and other non-tissue-destructive applications.
A conventional laser system generally includes three primary components: a laser medium that generates the laser light, a power supply that delivers energy to the laser medium in the form needed to excite the same to emit coherent light, and an optical cavity or resonator that concentrates the light to stimulate the emission of laser radiation. Laser emissions can range from ultraviolet wavelengths, visible light wavelengths, to infrared wavelengths, depending on the type of laser medium utilized, whether the medium comprises one or more gases, chemicals, dyes, metal vapors, and whether the laser is solid state, or semiconductor, etc.
In high output power surgical laser applications, solid state type lasers are often used in which the laser medium is comprised of a solid host crystalline or glass structure that includes at least one dopant material. Particular dopant materials and the corresponding emission wavelengths are well known in the art. For example, in hard and soft tissue ablation applications, neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers with an emission wavelength of about 1.064 μm, erbium-doped yttrium aluminum garnet (Er:YAG) lasers with an emission wavelength of 2.94 μm, and holmium-doped yttrium aluminum garnet (Ho:YAG) lasers are frequently utilized. Furthermore, erbium chromium doped yttrium, scandium, gallium garnet (Er, Cr:YSGG) lasers have been utilized successfully in medical treatment applications. Other laser media utilizing gasses such as carbon dioxide, argon, copper vapor lasers, and excimer media (e.g., using noble gas halides) have also been used with success.
During operation of a typical laser system, the laser medium (e.g., the doped solid host structure) is excited to a population inversion state with an optical pump such as a flash lamp that generates short-duration, intense, incoherent, full spectrum light. In the population inversion state, atoms of an elevated energy state exceed those of a lower energy state.
Instead of flash lamps, electrically powered diode lasers can also be utilized. The laser medium is disposed between two or more reflective mirrors that define an optical resonator. With each reflection off of the mirrors, the light is further stimulated by the optical pump, leading to its amplification. One of the mirrors is a partial reflector which allows some of the amplified light to exit the cavity as the laser emission, and can also be referred to as an output coupler. The laser output is typically pulsed by such techniques as Q-switching, which can result in substantially higher instantaneous laser power output, and continuous or quasi-continuous operation is also possible.
A laser diode can also be utilized in medical treatment applications. Similar in operation to light emitting diodes, the laser diode is comprised of a p layer and an n layer with an active photon emitting layer in between the p and n layers. Similar to the solid state laser, there are one or more reflectors as well as an output coupler, all of which are incorporated into the semiconductor assembly, with electrical current providing the stimulus to reach the population inversion state.
A conventional laser apparatus suitable for surgical applications is generally comprised of the aforementioned laser energy source and a separate handpiece coupled thereto that can be manually operated by the practitioner. In a basic implementation, the handpiece includes a tip that is in optical communication with the waveguide and the laser energy source. The tip directs the emitted laser onto a target tissue site, and varying shape configurations can yield different output profiles, including simple circular patterns. The laser emission can be directed at any angle that maximizes operator flexibility and comfort in accessing the target tissue site. The optical pathway can be offset from the connecting cable and handpiece axis using different reflector arrangements.
As briefly mentioned above, cutting and ablative efficacy largely depends upon the emitted wavelength and the absorptivity of that particular wavelength by the target tissue. Further, the intensity of the emission, along with the duration of the pulse, must be set to ensure that the tissue does not boil or vaporize, which can lead to greater injury and hemorrhaging. Following irradiation with a laser emission, the ablated tissue region is surrounded by a carbonization zone, a zone loosened by vacuoles, a coagulation zone, and a reversibly thermally damaged zone. The formation of the coagulation zone and the resultant hemostasis is advantageous in that tissue can be cut without bleeding.
In order to achieve the best results with the least amount of damage to the surrounding tissue, the laser emission parameters must be optimized for each clinical application. Most laser treatment devices are therefore dedicated to one operation, although supplemental features that do not involve laser emissions are also known. For example, a water supply line and an air supply line can be incorporated into the handpiece to deliver water and air to the target tissue area. This cools the target tissue and helps to remove debris. To further aid in the removal of debris, vacuum lines can be incorporated. The use of water and air to improve efficacy has not been limited to these objectives, and an alternative cutting mechanism by which laser energy is directed to a distribution of atomized fluid particles located in a volume of space away from the targeted tissue site has been developed and disclosed in, for example, Applicant's U.S. Pat. No. 5,741,247 to Rizoui, the disclosure of which is incorporated herein by reference. The laser energy is understood to interact with the atomized fluid particles causing the same to expand and impart mechanical cutting forces onto the target surface.
To the extent multiple laser emissions can be incorporated into a single laser system, existing laser systems such as those disclosed in U.S. Pat. No. 5,139,494 to Freiberg involve the use of a single laser catheter to the target tissue that is engaged to multiple sources of laser energy, each of which has a different therapeutic effect. The laser sources can be separately activated, and while concurrent operation is indicated, each of the laser energy sources is configured to operate as an independent unit to known effect. Alternatively, some others have contemplated the adjustment of the laser source to enable the selective emission of laser energy at different wavelengths and durations.
Accordingly, there is a need in the art for improved laser treatments utilizing concurrent laser emissions in order to achieve enhanced treatment capabilities that exceed those of such multiple laser emissions operated independently. There is also a need in the art for such laser treatments to achieve improved wound debridement, bacteria reduction and/or inactivation, biostimulation, tissue ablation, coagulation, and biofilm disruption, as well as combinations thereof in a single procedure